Core: Music Library

The music library system in Volumio 2 has two parts:

• Each service controller contains a flat array of all tracks in its service (tracklist). This tracklist can be scanned from the local filesystem or compiled from the online music service. Each entry contains things like URI, title, artist, etc. The service controller may generate this as-needed, or may cache this in memory or in a database.
• The Volumio music library is a data structure which contains entries for each genre, artist, album, track, etc. An entry for an album, for example, contains database links to its corresponding artists, tracks, etc. This allows for browsing of the music library. The library is stored in memory for fast access, but is a copy is also stored on disk to allow the library to be populated on startup.